1. Field of the Invention
The present invention generally relates to a high capacity hydrogen storage technology and, more particularly, to a high capacity hydrogen storage material and a method for making the same, in which a microporous material is oxidized to form channels of various sizes to communicate microporous structures to provide metal particles capable of decomposing hydrogen molecules into hydrogen atoms.
2. Description of the Prior Art
Since the advent of the industrial revolution in the late 18th and early 19th centuries, energy has been fundamental to the quality of our lives. With the increasing energy demand accompanying the growth of world population, we soon will be faced with fuel shortage and see more global-scale environmental degradation caused by the adverse effects of nowadays energy production and use, i.e., burning fossil fuels. Since the 1973 oil crisis, the developed countries have started to search for alternative energies, among which hydrogen energy has attracted tremendous attention because hydrogen can be obtained from water, which is abundant on earth. In addition, the hydrogen-fueled applications, such as fuel cells, are highly energy efficient and produce no greenhouse gases, such as carbon dioxide and etc, except water, which is environmentally friendly.
However, hydrogen exists in the form of gas under ambient condition and can only be liquefied below 33 K, which leads to considerable challenge and difficulty in storage and transportation. As a result, the lack of a proper storage method has become one of the main obstacles for the realization of hydrogen economy. Also due to the low gas density and strong repulsive force between hydrogen molecules, an ultra-high pressure tank is needed to store a large amount of hydrogen. This raises concerns over public safety giving rise to extra operating and maintenance cost on top of the compressing.
Hydrogen can also be stored in a liquid state. However, the boiling point of hydrogen molecules is −253° C. and therefore considerable amount of energy is needed to compress and liquefy hydrogen. The extra cost to maintain a cryogenic tank at such low temperature makes the onboard transportation impossible. Since the temperature of the environment for storing liquefied hydrogen is very low, a low-temperature apparatus is required. The liquefied hydrogen can thus be protected by liquid nitrogen to prevent from external heat. On the other hand, the exhaustion of hydrogen is also problematic.
Alternatively, hydrogen can be stored in solid-state materials, in which hydrogen is absorbed onto the surfaces of metal hydride or carbon based materials. Solid-state storage has the advantage in safety and ease of operating comparing to that using high pressure or cryogenic tanks. The drawback of the solid-state hydrogen storage materials is their low hydrogen uptake or release capacity at room temperature and many efforts have been devoted to increasing the storage capacity while keeping the adsorption and release processes reversible under ambient conditions. Conventional methods to increase the storage capacity have been aimed at increasing the density of adsorption sites by increasing the material's specific surface areas (SSAs). Alternatively, Yang and co-workers had disclosed in the J. Am. Chem. Soc. 128, 8136 (2006) and J. Phys. Chem. C 111, 11086 (2007) that the secondary spillover method by which a porous material was mixed with Pt doped activated carbon via a glucose bridge can enhanced the material's room temperature storage capacity from 0.4 to 4 wt %, an enhancement by a factor of 8. Here we provide a nanoporous material with modified surface chemistry and geometries of the pore structure that after being doped with transition metal particles exhibits even higher reversible hydrogen storage capacity at room temperature.